Question: Which of these numbers is composite? ${7,\ 19,\ 67,\ 73,\ 84}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 7, 19, 67, and 73 each have only two factors. The factors of 84 are 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, and 84. Thus, 84 is the composite number.